Predictors of surgical site infections and the clinical value of the Systemic Immune-Inflammation Index in children undergoing surgery

This study aimed to evaluate the determinants of postoperative complications in pediatric surgical patients and investigate whether the Systemic Immune-Inflammation Index (SII) independently predicts complication type in a predominantly acute abdominal pediatric surgical population. This retrospective study included patients aged 0 to 18 years who underwent surgical procedures between 2017 and 2024. Demographic characteristics, preoperative laboratory parameters, culture results, postoperative complications, and clinical outcomes were recorded. The primary outcome was postoperative complication class (local vs systemic). Secondary outcomes included in-hospital mortality, length of hospital stay, and readmission. Multivariable regression analyses were performed. A total of 307 pediatric patients were included; 64.17% were male. The majority underwent acute abdominal emergency surgery (89.54%). The most frequent culture growth site was the peritoneum (65.47%). Gram-negative microorganisms accounted for 94.46% of isolates, whereas Gram-positive organisms constituted 5.21%; fungal growth was observed in 1.30% of patients. Local complications were observed in 96.42% of patients, whereas systemic complications occurred in 3.58%. Overall mortality was 2.93%. Fever was significantly more common among non-survivors compared to survivors (77.78% vs 12.75%, P < .001), and systemic complications were associated with mortality (P = .040). Although SII values were higher in Gram-negative infections, SII did not independently predict complication type or mortality in this heterogeneous cohort. Gram-negative pathogens predominate in pediatric surgical infections. However, laboratory inflammatory indices, including SII, did not independently predict postoperative complication type or mortality. These findings suggest that clinical and perioperative factors play a more important role in determining outcomes in this predominantly acute abdominal pediatric surgical population.